Ossify

/ˈɒs.ɪ.faɪ/ verb hard

To become rigid and fixed in a particular way, especially in habits, attitudes, or institutions; literally, to turn into bone.

Once flexible about remote work, the company's policy slowly ossified into an inflexible five-day office rule.

Memory Trick

'Oss-' is Latin for 'bone,' as in 'ossuary' - ideas that ossify have hardened into bone, unable to bend anymore.